Plasma processing apparatus and plasma processing methdo

ABSTRACT

A plasma processing apparatus of an embodiment includes a chamber, an introducing part, a substrate electrode, a high-frequency power source, a low-frequency power source, and a switching mechanism. The introducing part introduces a process gas into the chamber. The substrate electrode is disposed in the chamber, a substrate is directly or indirectly mounted on the substrate electrode, and the substrate electrode includes a first and a second electrode elements alternately arranged. The high-frequency power source outputs a high-frequency voltage of 40 MHz or more for ionizing the process gas to generate plasma. The low-frequency power source outputs a low-frequency voltage of 20 MHz or less for introducing ions from the plasma. The switching mechanism applies the low-frequency voltage alternately to the first and the second electrode elements.

CROSS REFERENCE TO RELATED APPLICATION

This application is based upon and claims the benefit of priority fromJapanese Patent Application No. 2014-149241, filed on Jul. 22, 2014; theentire contents of which are incorporated herein by reference.

FIELD

Embodiments described herein relate generally to a plasma processingapparatus and a plasma processing method.

BACKGROUND

A plasma processing apparatus generates plasma, and makes ions in theplasma to be incident on a substrate (semiconductor wafer, for example),to thereby process the substrate. In a process of manufacturing asemiconductor device, when incident ions perform etching on a substrate,a trench, a via hole, a projecting portion and the like are formed.

Here, in the process of manufacturing the semiconductor device, it isimportant to perform fine control of processing shape, particularlyvertical processing of a sidewall of trench for securing electricalperformance of the semiconductor device.

However, it is not always easy to perform the fine control of processingshape, and it is usually the case that the sidewall of trench is notvertically formed, and is tapered, for example.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic configuration diagram of a plasma processingapparatus 10 according to a first embodiment.

FIG. 2 to FIG. 4 are perspective views each illustrating one example ofa configuration of a substrate electrode.

FIG. 5 is a diagram illustrating one example of voltage waveformsapplied to electrode elements.

FIG. 6 is a schematic diagram illustrating one example of ions which areincident on a wafer.

FIG. 7 is a schematic configuration diagram of a plasma processingapparatus 10 x according to a comparative example.

FIG. 8 is an enlarged sectional diagram illustrating a part of waferbefore being subjected to processing in a plasma processing apparatus.

FIG. 9 to FIG. 11 are enlarged sectional diagrams each illustrating astate of wafer after being subjected to etching.

FIG. 12 is a schematic configuration diagram of a plasma processingapparatus 10 a according to a modified example 1.

FIG. 13 is a schematic configuration diagram of a plasma processingapparatus 10 b according to a modified example 2.

FIG. 14 is a schematic diagram illustrating an induction coil 27.

FIG. 15 is a schematic configuration diagram of a plasma processingapparatus 10 c according to a second embodiment.

FIG. 16 is a diagram illustrating one example of voltage waveformsapplied to electrode elements.

FIG. 17 is a schematic configuration diagram of a plasma processingapparatus 10 d according to a modified example 3.

FIG. 18 is a schematic configuration diagram of a plasma processingapparatus 10 e according to a third embodiment.

FIG. 19 is a diagram illustrating a state of performing processing onsidewalls of trenches.

FIG. 20 is a diagram illustrating a state of performing processing on asidewall of via.

FIG. 21A to FIG. 21D are schematic diagrams each illustrating a state ofperforming processing while rotating a wafer.

FIG. 22A to FIG. 22D are schematic diagrams each illustrating a state ofperforming processing while rotating the wafer.

FIG. 23A to FIG. 23C are schematic diagrams each illustrating a state ofperforming processing while rotating the wafer.

FIG. 24A to FIG. 24D are schematic diagrams each illustrating a state ofperforming processing while rotating the wafer.

FIG. 25 is a partial configuration diagram of a plasma processingapparatus 10 f according to a modified example 4.

FIG. 26 is a partial configuration diagram of a plasma processingapparatus 10 g according to a modified example 5.

FIG. 27 is a partial configuration diagram of a plasma processingapparatus 10 h according to a modified example 6.

FIG. 28 and FIG. 29 are plan views each illustrating one example of aninternal electrode of an electrostatic chuck 42.

FIG. 30 is a schematic configuration diagram of a plasma processingapparatus 10 i according to a fourth embodiment.

FIG. 31 is a perspective view illustrating one example of aconfiguration of a substrate electrode 15 c.

FIG. 32 is a schematic configuration diagram of a plasma processingapparatus 10 j according to a fifth embodiment.

FIG. 33 is a plan view illustrating a state where the substrateelectrode 15 d is seen from the above.

FIG. 34A to FIG. 34D are schematic diagrams each illustrating a statewhere electrode elements Exy are classified into (selected as) groups.

FIG. 35 is a partial configuration diagram of a plasma processingapparatus 10 k according to a sixth embodiment.

FIG. 36 is a schematic configuration diagram of a plasma processingapparatus 10 l according to a seventh embodiment.

FIG. 37A and FIG. 37B are diagrams each illustrating one example of ascreen display.

FIG. 38A to FIG. 38C are graphs each illustrating a result of plasmasimulation of angle distributions of ions II which are incident on awafer Wf.

FIG. 39A to FIG. 39C are graphs each illustrating a result of plasmasimulation of angle distributions of ions II which are incident on thewafer Wf.

FIG. 40 is a diagram illustrating an electric field distribution of anentire calculation area.

FIG. 41 is a diagram illustrating evaluation points P1 to P5 withrespect to an electrode element E.

FIG. 42A to FIG. 42C are graphs each illustrating a result of plasmasimulation of angle distributions of ions II which are incident on thewafer Wf.

FIG. 43 is a diagram illustrating evaluation points Q1 to Q5 withrespect to a dielectric member DM.

FIG. 44 is a graph illustrating a relation between an electrode intervalD and a peak angle.

FIG. 45 is a graph illustrating a relation between an electrode width Wand a peak angle.

DETAILED DESCRIPTION

A plasma processing apparatus of an embodiment includes a chamber, anintroducing part, a substrate electrode, a high-frequency power source,a low-frequency power source, and a switching mechanism. The introducingpart introduces a process gas into the chamber. The substrate electrodeis disposed in the chamber, a substrate is directly or indirectlymounted on the substrate electrode, and the substrate electrode includesa first and a second electrode elements alternately arranged. Thehigh-frequency power source outputs a high-frequency voltage of 40 MHzor more for ionizing the process gas to generate plasma. Thelow-frequency power source outputs a low-frequency voltage of 20 MHz orless for introducing ions from the plasma. The switching mechanismapplies the low-frequency voltage alternately to the first and thesecond electrode elements.

Hereinafter, embodiments will be described in detail with reference tothe drawings.

First Embodiment

FIG. 1 is a schematic configuration diagram of a plasma processingapparatus 10 according to a first embodiment. The plasma processingapparatus 10 is a parallel plate type RIE (Reactive Ion Etching)apparatus.

The plasma processing apparatus 10 makes ions II in plasma PL to beincident on a wafer Wf to perform etching on the wafer Wf, therebyforming a trench, a via hole, a projecting portion and the like. Thewafer Wf is a substrate, which is, for example, a substrate ofsemiconductor (Si, GaAs or the like).

The plasma processing apparatus 10 is common to an ion implantationapparatus that implants ions, in a point that the ions II are made to beincident on the wafer Wf, but, the both pieces of apparatus aredifferent in the next point. In the plasma processing, an energy ofincident ions is lower than that in the ion implantation (about 10 k to500 keV in the ion implantation, and about 0 to 2000 eV in the plasmaprocessing). When compared to the ion implantation, the plasmaprocessing does not require a particular accelerator, and in the plasmaprocessing, ions II from plasma PL are introduced by a bias potentialapplied to a substrate electrode 15. For this reason, the plasma PL andthe substrate electrode 15 come close to each other in the plasmaprocessing apparatus 10, when compared to those in the ion implantation(about 10 cm or more in the ion implantation, and about several cm orless in the plasma processing).

The plasma processing apparatus 10 has a chamber 11, an exhaust port 12,a process gas introduction pipe 13, a susceptor 14, a substrateelectrode 15, a counter electrode 16, an RF high-frequency power source21 a, an RF low-frequency power source 21 b, matching devices 22 a and22 b, filters 23 a and 23 b, and a switching mechanism 24.

The chamber 11 maintains an environment required to perform processingon a wafer Wf.

The exhaust port 12 is connected to not-illustrated pressure regulatingvalve and exhaust pump. Gas in the chamber 11 is exhausted from theexhaust port 12, resulting in that the inside of the chamber 11 ismaintained in a high-vacuum state. Further, when process gas isintroduced from the process gas introduction pipe 13, a flow rate of gasflowed in through the process gas introduction pipe 13 and a flow rateof gas flowed out through the exhaust port 12 are balanced, resulting inthat a pressure in the chamber 11 is kept constant.

The process gas introduction pipe 13 is an introducing part whichintroduces process gas required to perform processing on the wafer Wf,into the chamber 11. The process gas is used for forming plasma PL. Byan electric discharge, the process gas is ionized to be turned intoplasma PL, and ions II in the plasma PL are used for performing etchingon the wafer Wf.

As the process gas, it is possible to appropriately use SF₆, CF₄, C₂F₆,C₄F₈, C₅F₈, C₄F₆, Cl₂, HBr, SiH₄, SiF₄ or the like, other than gas ofAr, Kr, Xe, N₂, O₂, CO, H₂ or the like.

Here, the process gas can be classified into deposition-type gas anddepositionless-type gas. The depositionless-type gas is gas thatperforms only an etching operation when performing processing on thewafer Wf. On the other hand, the deposition-type gas performs not onlythe etching operation but also an operation of forming a coating film(protective film) when performing processing on the wafer Wf.

By using the deposition-type gas as the process gas, it is possible toimprove a selection ratio of etching between an etching mask and anetching target (the wafer Wf or the like). Specifically, when thedeposition-type gas is used, the etching proceeds during which a coatingfilm is formed on the etching mask. As a result of this, an etching rateof the etching mask is reduced, and the selection ratio can be improved.

The classification of deposition type and depositionless type is notalways an absolute one. Rare gas (Ar, Kr, Xe) does not perform theoperation of forming the coating film almost at all, and thus it can beconsidered as pure depositionless-type gas, but, the other gas canperform the operation of forming the coating film in any way. Further, amagnitude relation between the etching operation and the operation offorming the coating film can be changed, based on a relation of amaterial and a shape of the etching mask and the etching target, aprocess pressure and the like.

Generally, Ar, Kr, Xe, H₂ and the like can be cited as thedepositionless-type gas. Further, C₂F₆, C₄F₆, C₄F₈, C₅F₈, SF₆, Cl₂, HBrcan be cited as the deposition-type gas. As an intermediate kind of gasbetween the deposition-type gas and the depositionless-type gas, therecan be cited N₂, O₂, CO, and CF₄.

The susceptor 14 is a holding part holding the wafer Wf, and has a chuckfor holding the wafer Wf. As the chuck, a mechanical chuck whichdynamically holds the wafer Wf, or an electrostatic chuck that holds thewafer Wf with the use of an electrostatic force can be used. Note thatexplanation will be made on details of the electrostatic chuck inlater-described modified example 6.

The substrate electrode 15 is an approximately plate-shaped electrodedisposed on the susceptor 14 and having an upper surface which is closeto or brought into contact with a lower surface of the wafer Wf.Specifically, the wafer Wf (substrate) is placed on the substrateelectrode 15 indirectly (the both are close to each other) or directly(the both are brought into contact with each other).

FIG. 2 is a perspective view illustrating one example of a configurationof the substrate electrode 15. As illustrated in FIG. 2, the substrateelectrode 15 corresponds to divided electrodes formed by being dividedin a plurality of pieces, and configured by two groups of electrodeelements E1 and E2 (first and second electrode element groups) which arealternately arranged.

Here, each of the two groups of electrode elements E1 and E2 has acenter axis along an axial direction A and an approximately column shapewith a width (a width of each of the electrode elements E1 and E2, here,a diameter) W, and the electrode elements E1 and E2 are arranged inapproximately parallel to each other with an interval D (a spatialdistance between the electrode elements E1 and E2) providedtherebetween. Note that the shape of each of the electrode elements E1and E2 is not limited to the approximately column shape, and the shapemay also be an approximately prism shape (approximately rectangularprism shape, for example).

At this time, it is preferable that the electrode interval D and theelectrode width (the diameter, in this case) W are small to some degree(for example, the electrode interval D is set to 5 mm or less). As willbe explained in later-described examples, an incident amount of ions IIhas a positional dependence. It can be considered that the incidentamount of ions II varies in a period corresponding to the interval D andthe electrode width W, by reflecting a periodic arrangement of theelectrode elements E1 and E2. For this reason, by reducing the intervalD and the electrode width W to some degree, the uniformity of plasmaprocessing is improved (spatial period of variation in the incidentamount of ions II is reduced).

FIG. 3 is a perspective view illustrating another example of theconfiguration of the substrate electrode. A substrate electrode 15 a haselectrode elements E1 and E2, and dielectric members DM.

The dielectric member DM is arranged between the electrode elements E1and E2. By the dielectric member DM, a voltage drop between theelectrode elements E1 and E2, and between the substrate electrode 15 andthe wafer Wf becomes small. As a result of this, a potential differencein a lateral direction is efficiently transmitted to the wafer Wf, whichenables to secure an oblique component of electric field. In order tosuppress the voltage drop, a dielectric constant of the dielectricmember DM is preferably high. For example, it is possible to set thedielectric constant to 7.0 or more (7.7 of alumina).

FIG. 4 is a perspective view illustrating another example of theconfiguration of the substrate electrode. A substrate electrode 15 b hasa dielectric member DM1, and a conductive layer EL. The conductive layerEL is disposed on the dielectric member DM1 having a plate shape. Forexample, the substrate electrode 15 b can be formed from a printedcircuit board.

The conductive layer EL has line patterns L1 and L2, and connectingportions C1 and C2. The line patterns L1 and L2 function as electrodeelements E1 and E2, respectively. The connecting portions C1 and C2electrically connect between the line patterns L1 and between the linepatterns L2, respectively.

At this time, a thickness of the conductive layer EL is sufficient to beequal to or less than about 1 mm, for example. Even if the line patternsL1 and L2 are thin, the electric field in the lateral direction, namely,the oblique component of the electric field can be generated, similar tothe case of using the electrode elements E1 and E2 each having a barshape. This is because an electric field that contributes to theelectric field in the lateral direction is not one caused by a potentialin a thickness direction of the line patterns L1 and L2, but one causedby a potential difference between the adjacent line patterns L1 and L2.

The counter electrode 16 is disposed to face the substrate electrode 15in the chamber 11, and one end thereof is set to a ground potential. Thecounter electrode 16 and the substrate electrode 15 form a parallelplate electrode.

The RF high-frequency power source 21 a generates an RF high-frequencyvoltage Va which is applied to the substrate electrode 15. The RFhigh-frequency voltage Va is an alternating voltage of relatively highfrequency which is used for generating plasma PL. A frequency fh of theRF high-frequency voltage Va is not less than 40 MHz nor more than 1000MHz, and is more preferably not less than 40 MHz nor more than 500 MHz(100 MHz, for example).

The RF low-frequency power source 21 b generates an RF low-frequencyvoltage Vb which is applied to the substrate electrode 15. The RFlow-frequency voltage Vb is an alternating voltage of relatively lowfrequency used for introducing the ions II from the plasma PL. Afrequency fl of the RF low-frequency voltage Vb is not less than 0.1 MHznor more than 20 MHz, and is more preferably not less than 0.5 MHz normore than 14 MHz (1 MHz, for example).

The matching devices 22 a and 22 b respectively match the impedance ofthe RF high-frequency power source 21 a and the RF low-frequency powersource 21 b to that of the plasma PL and the like.

The filter 23 a (HPF: High Pass Filter) prevents the RF low-frequencyvoltage Vb from the RF low-frequency power source 21 b from being inputinto the RF high-frequency power source 21 a.

The filter 23 b (LPF: Low Pass Filter) prevents the RF high-frequencyvoltage Va from the RF high-frequency power source 21 a from being inputinto the RF low-frequency power source 21 b.

The switching mechanism 24 applies a voltage in which the voltage fromthe RF high-frequency power source 21 a and the voltage from the RFlow-frequency power source 21 b are superposed (superposed voltage) VSto the electrode elements E1 and E2 in an alternate manner. As will bedescribed later, since there is a difference in the voltages applied tothe adjacent electrode elements E1 and E2, the ions II can be obliquelyincident on the wafer Wf from the plasma PL.

The switching mechanism 24 has switches SW1 and SW2, and a SW controller25.

Each of the switches SW1 and SW2 is a three-way switch, and selects toconnect the electrode elements E1 and E2 to either the superposedvoltage VS or a ground. The switches SW1 and SW2 function as first andsecond switches which switch the connection state of the electrodeelement groups E1 and E2 and the RF low-frequency power source 21 b. Aseach of the switches SW1 and SW2, a vacuum relay can be used, forexample.

The SW controller 25 is a switch controller controlling operations ofthe switches SW1 and SW2. When the SW controller 25 switches theswitches SW1 and SW2, it is possible to apply the superposed voltage VSto the electrode elements E1 and E2 in an alternate manner. Further, thesuperposed voltage VS can be applied to both of the electrode elementsE1 and E2 at the same time, or both of the electrode elements E1 and E2can be grounded at the same time.

It is preferable that when the superposed voltage VS is applied to theelectrode element E1, the electrode element E2 is grounded to a groundpotential. This is for maintaining the potential difference between theelectrode elements E1 and E2, and securing the oblique component of theelectric field. If the electrode element E2 is not grounded (if theelectrode element E2 is in a floating state where it is not connected toboth of the superposed voltage VS and the ground) when the superposedvoltage VS is applied to the electrode element E1, the potential of theelectrode element E2 is influenced by the potential of the electrodeelement E1 adjacent to the electrode element E2, resulting in that theoblique component of the electric field becomes weak. However, since theoblique component of the electric field is generated even in this case,it is also possible to consider to design such that the electrodeelement E2 is temporarily set to be in the floating state when thesuperposed voltage VS is applied to the electrode element E1.

Hereinafter, a switching operation of the switches SW1 and SW2 will bedescribed.

FIG. 5 illustrates one example of voltage waveforms V1 and V2 which areapplied to the electrode elements E1 and E2, respectively. Here, theswitches SW1 and SW2 are switched for every five periods of the RFlow-frequency voltage Vb. Specifically, a time period (period) T1 inwhich only the voltage V1 becomes the superposed voltage VS, and a timeperiod (period) T2 in which only the voltage V2 becomes the superposedvoltage VS, are alternately repeated. The periods (switching periods) T1and T2 are substantially the same (T).

It is also possible to design such that the switching period T (=T1, T2)is increased to be one corresponding to 10⁸ periods of the RFlow-frequency voltage Vb, for example. When the frequency fl of the RFlow-frequency voltage Vb is 10 MHz, the switching period T becomes 10seconds (=10⁸/(10*10⁶)).

A ratio between the switching period T and an oblique incidence processtime Tp (T/Tp) is preferably about 0.001 to 0.5. It is more preferablethat the ratio (T/Tp) is about 0.01 to 0.1 (specifically, the switchingis performed about 10 times to 100 times during a process). Thiscorresponds to a case where the switching period T is about 0.1 secondsto 3 seconds, when the oblique incidence process time Tp is assumed tobe about several tens of seconds, for example, 30 seconds.

Here, for easier understanding, a phase at the time of switching theswitches SW1 and SW2 and a phase of the RF low-frequency voltage Vb areset to be in a state of corresponding to each other. Actually, there isno need to make the phase at the time of switching the switches SW1 andSW2 and the phase of the RF low-frequency voltage Vb correspond to eachother. Specifically, there is no need to set the switching period T tobe an integral multiple of the period (=1/fl) of the RF low-frequencyvoltage Vb.

Here, the switching period T is set to be constant, but, it is alsopossible that the switching period T is temporally changed. As will bedescribed later, it is also possible to change the switching period Tbased on a progress of the process, and a relation with a rotation speedVr (reciprocal of rotation period Tr, Vr=1/Tr) of the substrate Wf to bedescribed later.

In FIG. 5, it is set that the switching of ON and OFF is instantaneouslyconducted at a boundary between the periods T1 and T2, for easierunderstanding. However, strictly speaking, it is also possible to designsuch that the switching is not conducted instantaneously, but isconducted via a transition time ΔT of about 0.1 seconds, for example.Specifically, it is possible to provide, between the time periods T1 andT2, a time period (transition time ΔT) in which both of the switches SW1and SW2 are ON. The plasma is securely maintained at the boundarybetween the switching periods T1 and T2, and further, the possibility ofabnormal discharge at the time of the switching is reduced.

At this time, when the SW controller 25 controls the switches SW1 andSW2, states 1) to 4) are repeated, the states being as follows:

1) the state in which the electrode element group E1 is connected to theRF low-frequency power source 21 b, and the electrode element group E2is not connected to the RF low-frequency power source 21 b;2) the state in which both of the electrode element groups E1 and E2 areconnected to the RF low-frequency power source 21 b;3) the state in which the electrode element group E1 is not connected tothe RF low-frequency power source 21 b, and the electrode element groupE2 is connected to the RF low-frequency power source 21 b; and4) the state in which both of the electrode element groups E1 and E2 areconnected to the RF low-frequency power source 21 b.

As described above, it is also possible to provide the time (transitiontime ΔT), at the boundary between the switching periods T1 and T2, inwhich the voltage is applied to the electrode elements E1 and E2 at thesame time. For example, a case where the RF low-frequency voltage Vb isapplied to the electrode element E1 for 10⁷ periods (1 second) and thenthe switching is made, is considered. At this time, the voltage isstarted to be applied also to the electrode element E2 from 0.1 seconds(10⁶ periods) before the switching. Further, a transition state in whichthe voltage is applied to both of the electrode elements E1 and E2, iscreated during the 0.1 seconds. After that, the application of voltageto the electrode element E1 is stopped, and the RF low-frequency voltageVb is applied only to the electrode element E2.

During the transition time ΔT, the oblique component of the electricfield is not generated. However, if the transition time ΔT issufficiently short when compared to the time (time period T) duringwhich the superposed voltage VS is applied only to one of the electrodeelements E1 and E2, an influence of the presence/absence of thetransition time ΔT exerted on the plasma processing can be ignored.

The 0.1 seconds of the transition time ΔT correspond to 10⁶ periods ofthe RF low-frequency voltage Vb whose frequency fl is 10 MHz(=f*0.1=10*10⁶*0.1).

Here, it is preferable that a ratio Rt between the transition time ΔTand the switching period T (=ΔT/T) is about 0.01 to 0.1. For example,when the RF low-frequency power source is switched for every 10 seconds,the transition time ΔT becomes 0.1 seconds to 1 second.

(Operation of Plasma Processing Apparatus 10)

In the chamber 11 in which an evacuation is conducted and a pressurereaches a predetermined pressure (0.01 Pa or less, for example), thewafer Wf is carried by a not-illustrated carrying mechanism. Next, thewafer Wf is held by the susceptor 14 with the use of the chuck. At thistime, the substrate electrode 15 is close to or brought into contactwith the wafer Wf.

Next, the process gas required to perform the processing on the wafer Wfis introduced from the process gas introduction pipe 13. At this time,the process gas introduced into the chamber 11 is exhausted at apredetermined rate from the exhaust port 12 by the not-illustratedpressure regulating valve and exhaust pump. As a result of this, thepressure in the chamber 11 is kept constant (about 1.0 to 6.0 Pa, forexample).

Next, the RF high-frequency voltage Va from the RF high-frequency powersource 21 a, and the RF low-frequency voltage Vb from the RFlow-frequency power source 21 b are applied to the substrate electrode15. The superposed voltage VS in which the RF high-frequency voltage Vaand the RF low-frequency voltage Vb are superposed is applied to theelectrode elements E1 and E2 in an alternate manner.

A density of the plasma PL is controlled by the RF high-frequencyvoltage Va from the RF high-frequency power source 21 a. An incidentenergy of ions II which are incident on the wafer Wf is controlled bythe RF low-frequency voltage Vb from the RF low-frequency power source21 b. The wafer Wf is etched by the ions II having an energy with avalue which is equal to or greater than a threshold value in the etchingprocessing of the wafer Wf.

FIG. 6 is a schematic diagram illustrating one example of ions II whichare incident on the wafer Wf.

The superposed voltage VS in which the RF high-frequency voltage Va andthe RF low-frequency voltage Vb are superposed is applied to theelectrode elements E1 and E2 in an alternate manner. Here, a componentof the RF high-frequency voltage Va does not exert a large influence onthe introduction of ions, based on a relation of frequency. For thisreason, it is possible to set such that the RF low-frequency voltage Vbis applied to the electrode elements E1 and E2 (substrate electrode 15)in an alternate manner.

When the RF low-frequency voltage Vb is applied between the substrateelectrode 15 and the counter electrode 16, there is generated anelectric field (vertical electric field) in a direction AP which isperpendicular to a plane of the substrate electrode 15 (wafer Wf) (referto FIG. 2). As a result of this, the ions II in the plasma PL areintroduced into the substrate electrode 15 (wafer Wf).

Here, the RF low-frequency voltage Vb is applied in an alternate manner,the potential between the adjacent electrode elements E1 and E2 isdifferent. For this reason, there is generated an electric field F in adirection parallel to the plane of the substrate electrode 15 (wafer Wf)and parallel to a direction Ah which is orthogonal to the axialdirection A of the electrode elements E1 and E2, in addition to theelectric field in the vertical direction (refer to FIG. 2 and FIG. 6).As a result of this, by corresponding to the electric field F, the ionsII are incident to have an incident angle θ (obliquely incident) withrespect to the vertical direction. When the ions II are obliquelyincident, it becomes possible to perform the etching on the wafer Wfwith high precision. Note that details of this will be described later.

The electric field F varies in accordance with the period of the RFlow-frequency voltage Vb. As a result of this, the incident angle θ ofions II periodically varies in accordance with the period of the RFlow-frequency voltage Vb.

As described above, by performing the switching of the RF low-frequencyvoltage, the ion with the incident angle θ in the positive direction andthe ion with the incident angle θ in the negative direction arealternately incident on the wafer Wf along the axial direction A.Specifically, in the present embodiment, the following becomes possible.

(1) The ions II can be obliquely incident on the wafer Wf at theincident angle θ. As will be described later, by using the obliquelyincident ions II, it becomes possible to perform processing with highprecision when forming the trench or the projecting portion, whilereducing the taper.

In particular, when forming the trench or the projecting portion alongthe axial direction A, the amount of ions II which are incident on asidewall of the trench or the like is increased, resulting in that thetaper can be reduced. Specifically, it is preferable to make a directionof the trench or the projecting portion (direction of processing line onthe wafer Wf) and the axial direction A of the electrode elements E1 andE2 coincide with each other.

(2) The ions II can be obliquely incident on both sides of the trench orthe projecting portion along the axial direction A. As a result of this,it is possible to reduce the taper on both sidewalls of the trench.

Comparative Example

FIG. 7 is a schematic configuration diagram of a plasma processingapparatus 10 x according to a comparative example. The plasma processingapparatus 10 x has the chamber 11, the exhaust port 12, the process gasintroduction pipe 13, a susceptor 14 x, a substrate electrode 15 x, thecounter electrode 16, the RF high-frequency power source 21 a, the RFlow-frequency power source 21 b, the matching devices 22 a and 22 b, andthe filters 23 a and 23 b.

The substrate electrode 15 x is different from the substrate electrode15, and has a plate shape with no electrode elements provided thereto(the substrate electrode 15 x is not divided). The RF high-frequencyvoltage Va from the RF high-frequency power source 21 a and the RFlow-frequency voltage Vb from the RF low-frequency power source 21 b aresuperposed to be applied to the substrate electrode 15 x, whichgenerates plasma PL and introduces ions II.

Since the substrate electrode 15 x is not divided, in the plasmaprocessing apparatus 10 x, no electric field F parallel to the plane ofthe wafer Wf is generated. For this reason, the ions II are incident,from the plasma PL, only in a direction perpendicular to the plane ofthe wafer Wf, and basically, no ions II which are obliquely incidentexist. As a result of this, it is difficult to perform precisionprocessing using the obliquely incident ions II.

(Comparison Between Embodiment and Comparative Example)

Hereinafter, a difference in the result of etching in the plasmaprocessing apparatus 10 according to the embodiment and the plasmaprocessing apparatus 10 x according to the comparative example will bedescribed.

FIG. 8 is an enlarged sectional diagram illustrating a part of wafer Wfbefore being subjected to processing in a plasma processing apparatus.On the wafer Wf, layers 31 and 32, and a mask 33 are formed. Materialsof the layers 31 and 32 are different materials, which are, for example,SiO₂ and Si. A material of the mask 33 is, for example, a resist orSiO₂, which is difficult to be etched, when compared to the layer 32.

FIG. 9 and FIG. 10 are enlarged sectional diagrams each illustrating astate after such a wafer Wf is etched in the plasma processing apparatus10 x. FIG. 9 illustrates a case where the depositionless-type gas isused as the process gas, and FIG. 10 illustrates a case where thedeposition-type gas is used as the process gas.

As illustrated in FIG. 9, when the depositionless-type gas is used asthe process gas, since the selection ratio between the mask 33 and thelayer 32 is small, an etching amount of the mask 33 is large, and itbecomes difficult to perform precision processing on the layer 32.

As illustrated in FIG. 10, when the deposition-type gas is used as theprocess gas, the selection ratio between the mask 33 and the layer 32becomes large, resulting in that the etching amount of the mask 33becomes small. However, the layer 32 is easily etched in the obliquedirection (the etched side surface is tapered). This is because aprotective film is formed on the side surface due to the deposition-typegas, and meanwhile, the side surface is difficult to be subjected to theetching operation performed by ions II which are vertically incident. Asdescribed above, when the deposition-type gas is used, in particular, itis possible to increase the selection ratio, but, it is difficult toperform vertical processing (precision processing).

Further, the number of ions II which hit against the etched side surface(sidewall of trench) is small, so that a residue or adherent is easilydeposited, which also makes it difficult to perform the precisionprocessing.

FIG. 11 is an enlarged sectional diagram illustrating a state after thewafer Wf is etched in the plasma processing apparatus 10. Here, a casewhere the deposition-type gas is used as the process gas, isillustrated. By using the deposition-type gas as the process gas, theselection ratio between the mask 33 and the layer 32 becomes large,resulting in that the etching amount of the mask 33 is small.

Further, the layer 32 is vertically etched (the etched side surface isnot tapered). The ions II are obliquely incident on both sides of theetched side surface (sidewall of trench), so that the taper on the sidesurface is reduced.

Here, there is no need to use the obliquely incident ions II in all ofthe processes of the formation of trench. It is also possible that theions II are vertically incident up to the middle of the formation oftrench, and thereafter, the ions II are obliquely incident.Specifically, it is also possible that, in accordance with the progressof the plasma processing process, the switching period T of thelow-frequency voltage Vb is changed, or the switching is stopped toapply the low-frequency voltage Vb to both of the electrode elements E1and E2. Note that details thereof will be described in third and fourthembodiments.

As described above, in the present embodiment, the ions II can beobliquely incident on the wafer Wf at the incident angle θ. As a resultof this, it becomes possible to perform the precision etching processingin which the vertical processing on the sidewall is easily performed,and the residue is difficult to be remained on the sidewall.

Modified Example 1

FIG. 12 is a schematic configuration diagram of a plasma processingapparatus 10 a according to a modified example 1. The plasma processingapparatus 10 a has the chamber 11, the exhaust port 12, a process gasintroduction pipe 13 a, the susceptor 14, the substrate electrode 15, acounter electrode 16 a, the RF high-frequency power source 21 a, the RFlow-frequency power source 21 b, the matching devices 22 a and 22 b, thefilters 23 a and 23 b, and the switching mechanism 24.

The counter electrode 16 a is a so-called showerhead, and has aninternal space and a plurality of openings. Process gas is introducedfrom the process gas introduction pipe 13 a to pass through the insideof the counter electrode 16 a, and is then introduced into the chamber11 from the plurality of openings of the counter electrode 16 a.Specifically, the counter electrode 16 a functions as an introducingpart introducing the process gas into the chamber 11.

The modified example 1 is different from the first embodiment in thatthe RF high-frequency power source 21 a is electrically connected not tothe substrate electrode 15 but to the counter electrode 16 a.Specifically, although the substrate electrode 15 rather serves togenerate the plasma PL in the first embodiment, the counter electrode 16a serves to generate the plasma PL in the modified example 1. Further, awall surface of the chamber 11 is grounded.

The modified example 1 is not largely different from the firstembodiment in the other points, so that the other explanation thereofwill be omitted.

Modified Example 2

FIG. 13 is a schematic configuration diagram of a plasma processingapparatus 10 b according to a modified example 2. The plasma processingapparatus 10 b has a chamber 11 b, the exhaust port 12, the process gasintroduction pipe 13, the susceptor 14, the substrate electrode 15, theRF high-frequency power source 21 a, the RF low-frequency power source21 b, the matching devices 22 a and 22 b, the filters 23 a and 23 b, theswitching mechanism 24, a window 111, and an induction coil 27. FIG. 14illustrates a state where the induction coil 27 is seen from the abovein FIG. 13.

The plasma processing apparatus 10 b is different from the plasmaprocessing apparatus 10 in that it does not have the counter electrode16 but has the window 111 and the induction coil 27.

The window 111 isolates the inside of the chamber 11 b from theatmosphere, and a magnetic field from the induction coil 27 is passedthrough the window 111. As the window 111, a plate of nonmagneticmaterial such as quartz, for example, is used. The induction coil 27 isdisposed on the outside of the chamber 11 b. When the high-frequencyvoltage from the RF high-frequency power source 21 a is applied to theinduction coil 27, a varying magnetic field is generated, resulting inthat the process gas in the chamber 11 b is ionized, and the plasma PLis generated. Note that a wall surface of the chamber 11 b is grounded.

The modified example 2 is not largely different from the firstembodiment in the other points, so that the other explanation thereofwill be omitted.

In each of the first embodiment and the modified examples 1 and 2, it ispossible to ionize the process gas to generate the plasma, with the useof the RF high-frequency voltage Va of 40 MHz or more. Specifically,even in a case where the plasma PL is generated without applying the RFhigh-frequency voltage Va to the substrate electrode 15, as illustratedin the modified examples 1 and 2, it is possible to control the incidentangle θ of the ions II by using the substrate electrode 15. Further, inthe case of the modified examples 1 and 2, the electrodes are different,so that it is also possible to use an RF high frequency of 10 MHz ormore.

Second Embodiment

FIG. 15 is a schematic configuration diagram of a plasma processingapparatus 10 c according to a second embodiment. The plasma processingapparatus 10 c has the chamber 11, the exhaust port 12, the process gasintroduction pipe 13, the susceptor 14, the substrate electrode 15, thecounter electrode 16, the RF high-frequency power source 21 a, the RFlow-frequency power source 21 b, the matching devices 22 a and 22 b, thefilters 23 a 1, 23 a 2, and 23 b, and the switching mechanism 24.

In the plasma processing apparatus 10, the on/off switching of both ofthe high-frequency voltage Va and the low-frequency voltage Vb isconducted.

In the plasma processing apparatus 10 c, the high-frequency voltage Vais constantly applied to the electrode elements E1 and E2, and on theother hand, the low-frequency voltage Vb is applied to the electrodeelements E1 and E2 in an alternate manner.

When the high-frequency voltage Va is kept applied, the density ofplasma PL can be maintained to a high density, and the amount ofincident ions II with respect to the substrate (wafer Wf) can bemaintained to a large amount, when compared to that in the plasmaprocessing apparatus 10. As described above, there is no need to performthe on/off switching of the high-frequency voltage Va, since thehigh-frequency voltage Va does not practically contribute to theintroduction of ions.

The switching mechanism 24 switches and applies the RF low-frequency(LF) voltage Vb from the RF low-frequency power source 21 b to theelectrode elements E1 and E2, in an alternate manner. For example, theswitching mechanism 24 applies the RF low-frequency voltage Vb to theelectrode elements in the order of the electrode elements E1, E2, E1,and E2, for every 10 seconds.

FIG. 16 is a diagram illustrating one example of voltage waveforms V1and V2 applied to the electrode elements E1 and E2. The voltagewaveforms V1 and V2 are respectively waveforms obtained by performingthe on/off switching of the RF low-frequency voltage Vb.

In FIG. 16, it is set that the switching of ON and OFF isinstantaneously conducted at the boundary between the periods T1 and T2,for easier understanding. However, it is also possible to provide thetransition time ΔT between the time periods T1 and T2, as describedabove.

Modified Example 3

FIG. 17 is a schematic configuration diagram of a plasma processingapparatus 10 d according to a modified example 3. The plasma processingapparatus 10 d has the chamber 11, the exhaust port 12, the process gasintroduction pipe 13, the susceptor 14, a substrate electrode 15 a, thecounter electrode 16, the RF high-frequency power source 21 a, the RFlow-frequency power source 21 b, an RF high-frequency power source 21 c,matching devices 22 a, 22 b, and 22 c, filters 23 a, 23 b, and 23 c, andthe switching mechanism 24.

The substrate electrode 15 a has electrode elements E1, E2, and E3. Theelectrode element E3 is arranged between the electrode elements E1 andE2. Specifically, the electrode elements E1, E3, E2, E3, E1, E3, E2, E3,E1, . . . are sequentially arranged.

The RF high-frequency power source 21 c, the matching device 22 c, andthe filter 23 c have functions corresponding to the functions of the RFhigh-frequency power source 21 a, the matching device 22 a, and thefilter 23 a, respectively.

The RF high-frequency power source 21 c generates an RF high-frequencyvoltage Vc applied to the electrode element E3. Specifically, only thehigh-frequency voltage Vc for generating the plasma PL is applied to theelectrode element E3.

The RF high-frequency voltage Vc is an alternating voltage of relativelyhigh frequency which is used for generating the plasma PL. A frequencyfh of the RF high-frequency voltage Vc is not less than 40 MHz nor morethan 1000 MHz, and is more preferably not less than 40 MHz nor more than500 MHz (100 MHz, for example).

The frequency of the RF high-frequency voltage Vc from the RFhigh-frequency power source 21 c can be set to a frequency same as thatof the RF high-frequency voltage Va from the RF high-frequency powersource 21 a. However, it is also possible that the frequencies of the RFhigh-frequency voltages Vc and Va are different.

The matching device 22 c matches the impedance of the RF high-frequencypower source 21 c to that of the plasma PL and the like.

The filter 23 c (HPF: High Pass Filter) prevents the RF low-frequencyvoltage Vb from the RF low-frequency power source 21 b from being inputinto the RF high-frequency power source 21 c.

In the modified example 2, the high-frequency voltage Va is kept appliedto both of the electrode elements E1 and E2, and only the low-frequencyvoltage Vb is switched to be applied to the electrode elements E1 andE2.

On the contrary, in the present modified example, the electrode elementE3 to which only the high-frequency voltage Vc for generating the plasmaPL is applied, is further arranged between the electrode elements E1 andE2. By the high-frequency voltage Vc which is constantly applied to theelectrode element E3, the density of the plasma PL is maintained to ahigh density, and a process rate is maintained.

Even if such a configuration is employed, the electric field F in thelateral direction is formed by a voltage difference among the adjacentelectrode elements (substrate electrode) E1, E2, and E3, resulting inthat the oblique incidence of ions II can be conducted.

Third Embodiment

FIG. 18 is a schematic configuration diagram of a plasma processingapparatus 10 e according to a third embodiment. The plasma processingapparatus 10 e has the chamber 11, the exhaust port 12, the process gasintroduction pipe 13, a susceptor 14 b, the substrate electrode 15, thecounter electrode 16, a wafer rotating mechanism 18, a terminationdetector 19, the RF high-frequency power source 21 a, the RFlow-frequency power source 21 b, the matching devices 22 a and 22 b, thefilters 23 a and 23 b, the switching mechanism 24, and a rotationcontroller 26.

In this case, the superposed voltage VS in which the voltages Va and Vbare superposed is applied to the substrate electrode 15 (electrodeelements E1 and E2) in an alternate manner, similar to the plasmaprocessing apparatus 10. On the contrary, it is also possible toappropriately change a combination of the voltages Va, Vb, and Vcapplied to the substrate electrode 15 and the counter electrode 16, asdescribed in the second embodiment and the modified examples 1 to 3.

When compared to the plasma processing apparatus 10, to the plasmaprocessing apparatus 10 e, the wafer rotating mechanism 18, thetermination detector 19, and the rotation controller 26 are added.

The wafer rotating mechanism 18 relatively rotates the wafer Wf withrespect to the substrate electrode 15, to thereby change a direction ofthe wafer Wf with respect to the axial direction A of the electrodeelements E1 and E2 of the substrate electrode 15. The rotation may beeither a temporary rotation or a continuous rotation, and can be changedin accordance with the progress of the process.

Further, it is also possible to design such that in accordance with theprogress of the process, the switching mechanism 24 changes the period(switching period T) in which the voltage is applied to the electrodeelement groups E1 and E2 in an alternate manner, or stops the alternateapplication to apply the voltage to both of the electrode element groupsE1 and E2. For example, after performing processing with the use of avertical incidence for one minute, it is possible to perform processingwith the use of an oblique incidence for 10 seconds as finish processingfor adjusting a shape. When the vertical incidence of ions is performed,the superposed voltage VS is applied to all of the electrode elements E1and E2. When the oblique incidence of ions is performed, the superposedvoltage VS is applied while switching the electrode elements E1 and E2.

At this time, a progress state of the process can be grasped by adetector such as the termination detector 19. Further, it is alsopossible to control the progress state of the process according to time,without using such a detector. This similarly applies to the otherembodiments as well.

Further, a combination of the switching period T and the rotation speedVr can employ various patterns. For example, the rotation speed Vr canbe set to 10 rotations per second. The rotation speed Vr in this case is600 rpm. The wafer may be rotated at a speed faster or slower than theabove rotation speed. The switching of the RF low-frequency voltage canbe performed once per second, for example. The switching may beperformed at a speed faster or slower than the above speed.

The termination detector 19 detects the termination of etching, based ona change in emission spectrum of the plasma PL, for example. Whencomposing materials of the layers 32 and 31 are different, the emissionspectrum of the plasma PL is changed due to the difference in thesecomposing materials, resulting in that the termination of etching of thelayer 32 (exposure of the layer 31) can be detected.

The rotation controller 26 controls the wafer rotating mechanism 18, andthe switching mechanism 24 in accordance with the transition of process(detection result in the termination detector 19 or time shift).

(1) The rotation controller 26 can control the wafer rotating mechanism18 in a manner as in the following a) and b).

a) The wafer Wf is rotated so that the direction of trench and the axialdirection A of the electrode elements E1 and E2 illustrated in FIG. 2coincide with each other (the directions are approximately parallel toeach other). By performing, after that, the plasma processing, it ispossible to improve the processing precision of the trench.

b) The wafer Wf is continuously rotated during the plasma processing. Bydesigning as above, it is possible to improve the processing precisionwithout depending on the direction of trench. Specifically, theprecision processing and vertical processing of a sidewall of via holeare realized.

FIG. 19 illustrates a state where sidewalls of trenches are processed,and FIG. 20 illustrates a state where a sidewall of via is processed.The layer 32 and the mask 33 are formed on the wafer Wf. In FIG. 19, themask 33 has a plurality of rectangular openings 331 along an axis Ay. InFIG. 20, the mask 33 has a plurality of circular openings 331.

By making the ions II to be incident from above the wafer Wf, a trenchTr is formed in FIG. 19, and a via hole Bh is formed in FIG. 20.Basically, the trench Tr is formed in FIG. 19, and the via hole Bh isformed in FIG. 20 due to the difference in shapes of the openings 331formed on the mask 33.

Here, it is set that the wafer Wf is not rotated in FIG. 19, bycorresponding to the first and second embodiments. On the other hand, itis set that the wafer Wf is rotated in FIG. 20, by corresponding to thethird embodiment. Further, it is set that in FIG. 19, the axis Aycoincides with the axis of the electrode element E illustrated in FIG. 2and FIG. 3.

At this time, in FIG. 19, the incident angle θ of the ions II is changedin which the axis Ay is set as a rotation axis. As a result of this, theions II are efficiently incident on the sidewall of the trench Tr. Asdescribed above, in order to efficiently form the trench Tr, it ispreferable that the axis of the opening 331 of the trench Tr and theaxis of the electrode element E are made to coincide with each other,and the wafer Wf is not rotated.

On the contrary, in FIG. 20, the wafer Wf is rotated, and the incidentangle of the ions II with respect to the axis Ax and that with respectto the axis Ay are symmetric (the ions II are obliquely incident fromall directions). As a result of this, it is possible to easily form thevia holes Bh symmetric with respect to a vertical axis Az of the waferWf. As described above, in order to form the via hole Bh with goodshape, it is preferable to rotate the wafer Wf.

Note that, as will be described in later-described fifth embodiment, asimilar effect can be achieved by rotating the electric field withoutchanging a relative angle between the wafer Wf and the substrateelectrode 15.

(2) The rotation controller 26 can control the switching mechanism 24 inthe following manner.

The RF low-frequency voltage Vb from the RF low-frequency power source21 b is applied to the respective electrode elements of the substrateelectrode 15 without performing the switching, up to the middle of theformation of the trench, to thereby realize the vertical incidence.Thereafter, the RF low-frequency voltage Vb is applied while beingswitched. Specifically, the switching mechanism 24 is controlled inaccordance with the progress of the plasma processing process, and theincident direction of the ions II is switched from the direction ofvertical incidence to the direction of oblique incidence.

By designing as above, it becomes possible to realize both of thesecurement of etching rate in a depth direction when the verticalincidence occurs and the reduction in taper when the oblique incidenceoccurs. The etching rate when the oblique incidence occurs is smallerthan that when the vertical incidence occurs. This is because, when theoblique incidence occurs, an area on the wafer Wf on which the ions areincident becomes large, and the number of incident ions per unit area isreduced, when compared to the time in which the vertical incidenceoccurs.

Note that for switching the time when the vertical incidence occurs andthe time when the oblique incidence occurs, the detection of terminationof etching of the layer 32 detected by the termination detector 19, thepassage of predetermined processing time, or a timing adjustment withthe switching period T can be utilized.

Hereinafter, an example of processing process of a hole H using therotation of the wafer Wf and the RF switching, will be described.

First, a progress of the processing of the hole H on the wafer Wf whenthe wafer Wf is rotated, will be described. At this time, it is set thatthe RF switching is not conducted.

As illustrated in FIG. 21A to FIG. 21D, it is set that in an initialswitching period T1, the voltage is applied to the electrode element E1,and the irradiation of ions II with oblique components in a direction ofarrow marks (right direction in the drawings) occurs. The hole H on thewafer Wf is also rotated together with the wafer Wf, and sidewalls(etching areas A1 to A4) of the hole H are sequentially and uniformlyetched in a circumferential direction (FIG. 21A to FIG. 21D). The waferin the state where the ions are incident in the obliquely rightdirection is repeatedly rotated an integer number of times (rotated 100times, for example). Here, when the rotation period Tr is set to 0.1seconds, the switching period T1 becomes 10 seconds.

Next, as a transition state before switching the voltage, the voltage isapplied to both of the electrode elements E1 and E2, and the wafer isrotated several times (rotated 10 times, for example) in the state wherethe ions are vertically incident. Note that it is also possible that astate where the voltage is not applied to both of the electrode elementsE1 and E2, and no etching is performed, is set as the transition state.When the rotation period Tr is 0.1 seconds, the transition time ΔTbecomes 1 second.

It is set that in the next switching period T2, the voltage is appliedto the electrode element E2, and ions with oblique components in adirection opposite to that of the arrow marks (left direction in thedrawings) are generated. Similarly, also in this case, the processuniformity in the circumferential direction is maintained during therotation (not illustrated). Further, during the switching period T2 (inwhich the wafer is rotated integer number of times same as that of theswitching period T1 and a time same as that of the switching period T1is provided), the ions II with oblique components in the direction ofarrow mark in the left direction (not illustrated) are irradiated.

Thereafter, in accordance with the process, by repeating the transitiontime ΔT, the switching period T1, the transition time ΔT, the switchingperiod T2 (for example, 1 second, 10 seconds, 1 second, 10 seconds), . .. , the hole H on the wafer is uniformly etched in the circumferentialdirection.

The switching periods T1 and T2, and the transition time ΔT may also bechanged in the middle of the process. Although the switching periods T1and T2 do not necessarily have to be the same, basically, a nearly equalperiod of time is assumed as the switching periods T1 and T2.

By setting each of the switching periods T1 and T2, and the transitiontime ΔT to one corresponding to the integer number of times of rotationof the wafer Wf, it is possible to simplify the relation of the rotationspeed Vr and the switching periods T1 and T2.

Note that the switching periods T1 and T2 do not necessarily have tocorrespond to the integer number of times of rotation. Specifically, itis also possible to change, in the middle of one rotation of the waferWf, the state where the ions are incident in the obliquely rightdirection (T1) and the state where the ions are incident in theobliquely left direction (T2). However, in this case, there is a need toadjust the rotation speed Vr and a timing of the switching. Depending ona relation of these, the process uniformity in the circumferentialdirection is not always achieved.

The following a) to c) describe some examples.

a) Case where the switching period T (T1, T2) is 0.5n times the rotationperiod Tr (refer to FIG. 22A to FIG. 22D)

The case where the switching period T is 0.5n (n=1, 3, 5, . . . oddnumber) times the rotation period Tr is considered. Here, concretely, acase where the state where the ions are incident in the obliquely rightdirection and the state where the ions are incident in the obliquelyleft direction are switched for every ½ rotations, is considered.

FIG. 22A to FIG. 22D illustrate states where the wafer Wf makes 0rotation, 0.5 rotations, 1.0 rotation, and 1.5 rotations, respectively.The state where the wafer Wf makes 1.5 rotations in FIG. 22D shifts to astate where the wafer Wf makes 2.0 rotations corresponding to FIG. 22A.FIG. 22A to FIG. 22B, FIG. 22B to FIG. 22C, and FIG. 22C to FIG. 22Dcorrespond to the switching periods T1, T2, and T1, respectively.Specifically, at a moment illustrated in FIG. 22A to FIG. 22D, thedirection of ions II is switched from the left to the right, or from theright to the left.

In the switching periods T1, T2, and T1, the areas A1, A2, and A3 areetched, respectively.

In the switching period T1 (when ions in the right direction areirradiated), the wafer Wf makes a half rotation, and thereafter, theswitching period T2 (irradiation of ions in the left direction) isstarted. In this case, the same sides (the areas A1 and A2) of the holeH are shaved in both of the first-half rotation and the last-halfrotation. This causes a non-uniform etching, which is not favorable.

Note that although it is assumed that the switching is instantaneouslyconducted in FIG. 22A to FIG. 22D, in reality, the transition time ΔT isrequired as described above, and depending on the setting of thetransition time ΔT, the process uniformity in the circumferentialdirection changes. For example, if the transition time ΔT is set to onecorresponding to the integer number of times of rotation, the uniformityin the circumferential direction becomes one same as that in the casewhere the transition time ΔT is not provided. When the transition timeΔT is shorter than the switching periods T1 and T2, a switching positionis deviated by the transition time ΔT (not illustrated).

b) Case where the switching period T is ⅓ times the rotation period Tr(refer to FIG. 23A to FIG. 23C)

The case where each of the switching periods T1 and T2 is ⅓ times therotation period Tr is considered.

FIG. 23A to FIG. 23C illustrate states where the wafer Wf makes 0rotation, ⅓ rotations, and ⅔ rotations, respectively. The state wherethe wafer Wf makes ⅔ rotations in FIG. 23C shifts to a state where thewafer Wf makes one rotation corresponding to FIG. 23A. FIG. 23A to FIG.23B, and FIG. 23B to FIG. 23C correspond to the switching periods T1 andT2, respectively. Specifically, at a moment illustrated in FIG. 23A toFIG. 23C, the direction of ions II is switched from the left to theright, or from the right to the left.

In the switching periods T1 and T2, the areas A1 and A2 are etched,respectively.

As illustrated in FIG. 23A to FIG. 23C, parts of etching positions A1and A2 on the circumference are overlapped. However, the overlappedparts are deviated each time the rotation and the switching arerepeated. When several tens to several hundreds of times of rotationsare conducted, the process uniformity in the circumferential directionis maintained in consequence.

Note that when the transition time ΔT is taken into consideration, theuniformity in the circumferential direction is influenced by the lengthof the transition time ΔT, resulting in that an additional adjustmentbecomes required.

c) Case where the switching period T is ¼ times the rotation period Tr(refer to FIG. 24A to FIG. 24D)

The case where the switching period T is ¼ times the rotation period Tris considered.

FIG. 24A to FIG. 24D illustrate states where the wafer Wf makes 0rotation, ¼ rotations, 2/4 rotation, and ¾ rotations, respectively. Thestate where the wafer Wf makes ¾ rotations in FIG. 24D shifts to a statewhere the wafer Wf makes one rotation corresponding to FIG. 24A. FIG.24A to FIG. 24B, FIG. 24B to FIG. 24C, and FIG. 24C to FIG. 24Dcorrespond to the switching periods T1, T2, and T1, respectively.Specifically, at a moment illustrated in FIG. 24A to FIG. 24D, thedirection of ions II is switched from the left to the right, or from theright to the left.

In the switching periods T1, T2, and T1, the areas A1, A2, and A3 areetched, respectively.

In this case, the whole surface of the wafer Wf is shaved when the waferWf makes one rotation, so that the uniformity in the etching directioncan be secured.

When the transition time ΔT is taken into consideration, the uniformityin the circumferential direction is influenced by the length of thetransition time ΔT.

As described above, the concrete examples regarding the switchingperiods T1 and T2, and the rotation period Tr are described as in thecases a to c, but, cases other than the above can also be considered. Asdescribed in the concrete examples, when the incident direction of ionsII is switched in the middle of the rotation, there is an unfavorablerelation among the switching period T, the rotation period Tr, and thetransition time ΔT. Practically, it is preferable that each of theswitching periods T1 and T2, and the transition time ΔT is an integralmultiple of the rotation period Tr.

The rotation period Tr is assumed to be fallen within a range of about0.01 seconds to 100 seconds. The transition time ΔT is assumed to beabout several times to several tens of times the rotation period Tr. Itis preferable that the transition time ΔT is as small as possible withrespect to the switching periods T1 and T2 so that a long period of timein which the oblique incidence is effective can be secured. This isbecause the vertical incidence or the etching is not conducted duringthe transition time ΔT.

Note that the applied voltage is a sine wave, so that strictly speaking,the voltage changes during one period of high frequency or lowfrequency, and in accordance with the change, the oblique component alsovaries. However, the variation and a time scale of the rotation aredifferent by at least 10⁵ or more, so that an influence of the variationof the oblique component in the period of low frequency can be ignored.

Modified Examples 4 to 6

Hereinafter, modified examples of the third embodiment (modifiedexamples 4 to 6) will be described. The modified examples 4 to 6 are forspecifically explaining a mechanism that relatively rotates between thewafer Wf and the substrate electrode 15. Accordingly, each of themodified examples is illustrated by a partial configuration diagramwhich omits a part other than a part of the rotating mechanism.

(1) Modified Example 4

FIG. 25 is a partial configuration diagram of a plasma processingapparatus 10 f according to the modified example 4. The plasmaprocessing apparatus 10 f has a susceptor 141, a substrate electrodeblock 142, and a motor 41, in place of the susceptor 14, and the waferrotating mechanism 18 in the plasma processing apparatus 10 e.

The motor 41 is provided for rotating the susceptor 141, and has arotating shaft 411, a rotor 412, a stator 413, a side plate 414, and abottom plate 415.

The rotating shaft 411, the rotor 412, and the stator 413 form arotating mechanism. The rotating shaft 411 is connected to the susceptor141. The rotating shaft 411 is formed in a cylindrical shape, and in theinside thereof, a shaft of the substrate electrode block 142 isdisposed. The rotor 412 is a magnet disposed on a side surface of therotating shaft 411. The stator 413 is an electromagnet disposed on theoutside of the side plate 414 so as to approximate to the rotor 412 withthe side plate 414 therebetween. By a magnetic force generated byperiodically changing the north pole and the south pole of the magneticfield of the stator 413, the rotor 412 rotates with respect to thestator 413. As a result of this, the rotating shaft 411 and the rotor412 in the chamber 11 (vacuum side), and the stator 413 on the outsideof the chamber 11 (atmosphere side) are separated from each other.

Note that in this case, the rotor 412 uses the permanent magnet and thestator 413 uses the electromagnet, but, it is also possible that therotor 412 uses the electromagnet and the stator 413 uses the permanentmagnet, or both of the rotor 412 and the stator 413 use theelectromagnet. The same applies to the following modified examples 5 and6.

The susceptor 141 is connected to the rotating shaft 411 in a state ofholding the wafer Wf on its upper surface, and is rotated by therotating mechanism. As a result of this, the wafer Wf is rotated by therotating mechanism.

The susceptor 141 has an internal space for holding the substrateelectrode block 142.

The substrate electrode block 142 is disposed in the inside of thesusceptor 141, and is not rotated by being fixed to the bottom plate415.

The voltage waveforms V1 and V2 (the voltage waveforms in each of whichthe RF high-frequency voltage Va and the RF low-frequency voltage Vb aresuperposed) are supplied to the substrate electrode 15 in the chamber 11from the RF high-frequency power source 21 a and the RF low-frequencypower source 21 b disposed on the outside of the chamber 11.

By rotating the wafer Wf, oblique ions are incident on the wafer Wf fromall directions.

(2) Modified Example 5

FIG. 26 is a partial configuration diagram of a plasma processingapparatus 10 g according to the modified example 5. The plasmaprocessing apparatus 10 g has a susceptor 141 a, a substrate electrodeblock 142 a, and a motor 41 a, in place of the susceptor 14 b and thewafer rotating mechanism 18 in the plasma processing apparatus 10 e.

The motor 41 a is provided for rotating the substrate electrode block142 a, and has a rotating shaft 411 a, the rotor 412, the stator 413,the side plate 414, the bottom plate 415, ring electrodes 416, and brushelectrodes 417.

The rotating shaft 411 a, the rotor 412, and the stator 413 form arotating mechanism. The rotating shaft 411 a is connected to thesubstrate electrode block 142 a. The rotor 412 is a magnet disposed on aside surface of the rotating shaft 411 a. The stator 413 is anelectromagnet disposed on the outside of the side plate 414 so as toapproximate to the rotor 412 with the side plate 414 therebetween. By amagnetic force generated by periodically changing the north pole and thesouth pole of the magnetic field of the stator 413, the rotor 412rotates with respect to the stator 413. As a result of this, therotating shaft 411 a and the rotor 412 in the chamber 11 (vacuum side),and the stator 413 on the outside of the chamber 11 (atmosphere side)are separated from each other.

The ring electrode 416 and the brush electrode 417 are provided forsecuring an electrical connection with respect to the substrateelectrode 15 during the rotation of the rotating shaft 411 a, by beingbrought into contact with each other in a state where they are slidrelative to each other. The ring electrode 416 is a ring-shapedelectrode disposed by being fixed to an outer periphery of the rotatingshaft 411 a. The brush electrode 417 is a brush-shaped electrode whichis brought into contact with the ring electrode 416 by sliding relativeto the ring electrode 416, during the rotation of the rotating shaft 411a.

The voltage waveforms V1 and V2 from the switching mechanism 24 aresupplied to the substrate electrode 15 in the chamber 11 from the RFhigh-frequency power source 21 a and the RF low-frequency power source21 b disposed on the outside of the chamber 11 via the brush electrodes417 and the ring electrodes 416.

The susceptor 141 a has an internal space for holding the substrateelectrode block 142 a. The susceptor 141 a is not rotated by being fixedto the chamber 11.

The substrate electrode block 142 a is disposed in the inside of thesusceptor 141 a. The substrate electrode block 142 a is connected to therotating shaft 411 a, and is rotated by the rotating mechanism. As aresult of this, the substrate electrode 15 is rotated by the rotatingmechanism.

By rotating the substrate electrode 15, an electric field distributiongenerated on the wafer Wf is rotated, resulting in that oblique ions areincident on the wafer Wf from all directions.

Note that the plasma processing apparatus 10 g may also have anelectrostatic chuck. A DC voltage is connected to a rotating part via abrush current introduction electrode, and is supplied to a DC electrode.

(3) Modified Example 6

FIG. 27 is a partial configuration diagram of a plasma processingapparatus 10 h according to the modified example 6. The plasmaprocessing apparatus 10 h has a susceptor 141 b, a substrate electrodeblock 142 b, a motor 41 b, an electrostatic chuck 42, a DC power source43, and a cooling medium supply unit 44, in place of the susceptor 14and the wafer rotating mechanism 18 in the plasma processing apparatus10 e.

The motor 41 b is provided for rotating the substrate electrode block142 b, and has the rotating shaft 411, the rotor 412, the stator 413,the side plate 414, the bottom plate 415, a ring electrode 416 a, abrush electrode 417 a, and an opening 418.

The rotating shaft 411, the rotor 412, and the stator 413 form arotating mechanism. The configuration, the operation and the like of therotating mechanism are substantially similar to those of the modifiedexample 4, so that detailed explanation thereof will be omitted.

The ring electrode 416 a and the brush electrode 417 a are provided forsecuring an electrical connection with respect to an internal electrodeof the electrostatic chuck 42 during the rotation of the rotating shaft411, by being brought into contact with each other in a state where theyare slid relative to each other. The ring electrode 416 a is aring-shaped electrode disposed by being fixed to an outer periphery ofthe rotating shaft 411. The brush electrode 417 a is a brush-shapedelectrode which is brought into contact with the ring electrode 416 a bysliding relative to the ring electrode 416 a, during the rotation of therotating shaft 411.

The electrostatic chuck 42 is provided for electrostatically attractingthe wafer Wf, and has a plurality of openings 421. The internalelectrode of the electrostatic chuck 42 is a kind of mesh-shapedelectrode, and functions as an attraction electrode having a pluralityof openings.

FIG. 28 and FIG. 29 are plan views each illustrating one example of theinternal electrode of the electrostatic chuck 42. In FIG. 28,square-shaped openings (air gaps) 421 are arranged in lines in thevertical and horizontal two directions (a kind of mesh-shapedelectrode). In FIG. 29, rectangular (line-shaped) openings (air gaps)421 are arranged in lines (a kind of line-shaped electrode). In FIG. 28and FIG. 29, the rectangular openings are arranged in two directions andin one direction, respectively.

When the electrostatic chuck 42 is used for making the susceptor holdthe substrate, in the plasma processing apparatus 10 x, a low-frequencyvoltage for introducing ions and a DC voltage for electrostaticattraction are superposed to be applied to the substrate electrode 15 x.Specifically, the substrate electrode 15 x and the internal electrode ofthe electrostatic chuck are integrated.

When a DC voltage is superposed to be applied by using one DC powersource which is not illustrated, in the first to third embodiments, itis required to provide a filter mechanism with the use of a capacitanceand an inductance, for example, in order to prevent the low-frequencyvoltage from the low-frequency power source for each of the electrodegroups from flowing into the different electrode groups via the DC powersource to be connected (similar to the HPF (high pass filter) in thecase of superposing the high-frequency voltage).

Further, when there is provided the mechanism of relatively rotatingbetween the wafer Wf and the substrate electrode 15 as described in themodified examples 4 and 5, it becomes difficult to attract the wafer Wfby using the same electrode since the wafer Wf and the substrateelectrode 15 are separated. In this case, it becomes necessary toadditionally provide the electrode for electrostatic attraction in thevicinity of the wafer Wf, as described in the modified example 6.

The line-shaped openings 421 illustrated in FIG. 29 are suitable for acase where the susceptor 14, the substrate electrode 15 and the like arenot rotated as described in the first and second embodiments. In thiscase, an axis of the opening 421 is preferably made to coincide with theaxis Ay of the opening 331 of the trench Tr and the axis of theelectrode element E (refer to FIG. 2, FIG. 3 and FIG. 19).

In this case, the shape of the opening 421 is set to a rectangularshape, but, it is also possible to employ a circular opening, anelliptical opening and the like, in place of the rectangular opening.

As illustrated in FIG. 28 and FIG. 29, the opening 421 has a width D(which corresponds to the electrode interval D in FIG. 2). As will bedescribed later, the width D is preferably 2 to 5 mm.

The DC power source 43 supplies a DC voltage to the internal electrodeof the electrostatic chuck 42, thereby making the electrostatic chuck 42electrostatically attract the wafer Wf. The DC voltage from the DC powersource 43 is supplied to the internal electrode of the electrostaticchuck 42 in the susceptor 141 b via the brush electrode 417 a and thering electrode 416 a.

The cooling medium supply unit 44 supplies a cooling medium C forcooling the wafer Wf. From the point of view of inertness, thermalconductivity and the like, it is preferable to use He, for example, asthe cooling medium C.

The susceptor 141 b has openings 143 for introducing the cooling mediumC. The bottom plate 415 has the opening 418 for introducing the coolingmedium C into the susceptor 141 b. The cooling medium C supplied fromthe cooling medium supply unit 44 passes through the opening 418 and theinside of the susceptor 141 b to be supplied to a rear surface of thewafer Wf through the openings 143, thereby cooling the wafer Wf. Thecooling medium C after cooling the wafer Wf is released in the chamber11, and is exhausted to the outside from the exhaust port 12.

Fourth Embodiment

FIG. 30 is a schematic configuration diagram of a plasma processingapparatus 10 i according to a fourth embodiment. The plasma processingapparatus 10 i has the chamber 11, the exhaust port 12, the process gasintroduction pipe 13, a susceptor 14 c, a substrate electrode 15 c, thecounter electrode 16, the termination detector 19, the RF high-frequencypower source 21 a, the RF low-frequency power source 21 b, the matchingdevices 22 a and 22 b, the filters 23 a and 23 b, the switchingmechanism 24, a controller 26 c, and switches SW3 and SW4. Note that theillustration of capacitors is omitted for easier view.

When compared to the plasma processing apparatus 10 e, the plasmaprocessing apparatus 10 i does not have the wafer rotating mechanism 18,and uses the substrate electrode 15 c, in place of the substrateelectrode 15.

FIG. 31 is a perspective view illustrating one example of aconfiguration of the substrate electrode 15 c. The substrate electrode15 c is formed of electrode elements E11 and E12, and electrode elementsE21 and E22, which are arranged in the up and down directions. Here, itcan be considered that the electrode elements E11 and E12 form a firstelectrode element group, and the electrode elements E21 and E22 form asecond electrode element group. Specifically, the substrate electrode 15c has these first and second electrode element groups.

The electrode elements E11 and E12 correspond to the electrode elementsE1 and E2 in the first embodiment, and are alternately arranged along anaxial direction A1.

The electrode elements E21 and E22 are alternately arranged along anaxial direction A2 under the electrode elements E11 and E12. These axialdirections A1 and A2 are mutually different (the directions areorthogonal to each other, for example).

By switching, with the use of the switching mechanism 24 and thecontroller 26 c, either on or off in the respective electrode elementsE11 and E12, and electrode elements E21 and E22, oblique components arerespectively obtained. Further, by applying the voltage to both of theE11 and E12 or both of the E21 and the E22, the vertical incidence canbe realized.

As described above, the switches SW3 and SW4 switch the electrodeelements E11 and E12, and the electrode elements E21 and E22, to applythe superposed voltage VS in which the RF high-frequency voltage Va andthe RF low-frequency voltage Vb are superposed.

Since the axial direction A1 of the electrode elements E21 and E22 isdifferent from the axial direction A2 of the electrode elements E11 andE12, it is possible to simultaneously or independently realize theoblique components in the two directions, resulting in that it ispossible to deal with processing of a shape having trenches in multipledirections.

Fifth Embodiment

FIG. 32 is a schematic configuration diagram of a plasma processingapparatus 10 j according to a fifth embodiment.

The plasma processing apparatus 10 j has the chamber 11, the exhaustport 12, the process gas introduction pipe 13, a susceptor 14 d, asubstrate electrode 15 d, the counter electrode 16, a shift register 51,a controller 52, the RF high-frequency power source 21 a, the RFlow-frequency power source 21 b, the matching devices 22 a and 22 b, thefilters 23 a and 23 b, and the switching mechanism 24.

FIG. 33 is a plan view illustrating a state where the substrateelectrode 15 d is seen from the above. The substrate electrode 15 d haselectrode elements Exy which are arranged in lines in the vertical andhorizontal two directions. Here, although the electrode elements Exy arearranged in the vertical and horizontal two directions, which areorthogonal to each other, the directions are not necessarily required tobe orthogonal to each other. It is sufficient if the electrode elementsExy are arranged in lines in mutually different first and seconddirections.

Here, the electrode element Exy has a rectangular shape (square shape)when seen from the above, but, it may also be formed to have a circularshape.

The shift register 51 performs a selection to connect the electrodeelements Exy to either the switch SW1 or the switch SW2. The shiftregister 51 functions as a selecting unit that selects, from a pluralityof electrode elements, the plurality of electrode element groupsarranged along one direction. The shift register 51 selects theelectrode elements Exy so that the electrode elements Exy are classifiedinto two on/off groups (line-shaped groups) which are parallel to eachother (arranged in approximately the same direction θ), for example.

FIG. 34A to FIG. 34D illustrate cases where the electrode elements Exyare classified into (selected as) groups G11 and G12, groups G21 andG22, groups G31 and G32, and groups G41 and G42, in which the directionθ corresponds to 0°, 45°, 90°, and 135°, respectively.

In this case, the shift register 51 selects any of first and secondelectrode element groups (the groups G11 and G12, the groups G21 andG22, the groups G31 and G32, and the groups G41 and G42) which arearranged along a first direction (0° direction), a second direction (90°direction), a third direction being an intermediate direction betweenthe first and second directions (45° direction), and a fourth directionbeing an intermediate direction between the second and first directions(135° direction), respectively.

Here, although the third direction is set to the direction which isright between the first and second directions, it is also possible toset an arbitrary intermediate direction between the first and seconddirections. Further, it is also possible to set an arbitraryintermediate direction between the second and first directions, as thefourth direction. Further, it is also possible to set a plurality ofintermediate directions between the first and second directions.

The controller 52 controls the shift register 51 to change the groupingof the electrode elements Exy so that the direction θ sequentiallyrotates. For example, it is set that the groups G11 and G12, the groupsG21 and G22, the groups G31 and G32, and the groups G41 and G42 in FIG.34A to FIG. 34D are periodically and repeatedly selected. This meansthat the direction θ in which the electrode elements Exy are groupedrotates. The groups G11 and G12 correspond to both cases where 0 equalsto 0° and where 0 equals to 180°, so that when the groups G11 and G12are selected after the selection of the groups G41 and G42, this meansthat the electric field from the substrate electrode 15 d is rotated.

By rotating the line-shaped groups, the electric field distributiongenerated on the wafer Wf is rotated, resulting in that oblique ions areincident on the wafer Wf from all directions. Specifically, it becomespossible to achieve an effect similar to that achieved when the wafer Wfis rotated.

As described above, the controller 52 controls the switching mechanism24, to thereby change the connection relation of the electrode elementsExy and the switches SW1 and SW2 in time series. Specifically, thecontroller 52 makes the arranging direction θ of the selected electrodeelements Exy to be temporally changed.

Sixth Embodiment

FIG. 35 is a schematic configuration diagram of a plasma processingapparatus 10 k according to a sixth embodiment. The plasma processingapparatus 10 k has the chamber 11, the exhaust port 12, the process gasintroduction pipe 13, the susceptor 14 b, the substrate electrode 15,the counter electrode 16, the wafer rotating mechanism 18, thetermination detector 19, the RF high-frequency power source 21 a, the RFlow-frequency power source 21 b, the matching devices 22 a and 22 b, thefilters 23 a and 23 b, and the rotation controller 26.

In this case, the superposed voltage VS in which the voltages Va and Vbare superposed is applied to one side of the substrate electrode 15(electrode element E1 or E2), and the other side of the electrode groupsis grounded. Accordingly, the oblique incident process only in theone-side direction is performed. Note that it is also possible toconstantly apply the high-frequency voltage Va to both of the electrodegroups, as in the second embodiment.

As already illustrated in FIG. 21, when the rotating mechanism isintroduced, the switching mechanism of the applied voltage is notnecessarily required. By constantly performing only the one-side obliqueincidence as in the present embodiment, the process uniformity in thecircumferential direction is achieved without depending on the rotationperiod.

Seventh Embodiment

FIG. 36 is a diagram illustrating a plasma processing apparatus 10 laccording to a seventh embodiment. The plasma processing apparatus 10 lhas a display/input unit 27, and a display controller 28.

The display/input unit 27 is a touch display, for example, a liquidcrystal display device which enables both of a display and an input ofinformation. The display/input unit 27 can perform display bydistinguishing between the vertical incidence and the oblique incidenceof ions.

The display controller 28 controls the display and the input in thedisplay/input unit 27.

A process condition is input into the plasma processing apparatus 10 lby using the display/input unit 27, and the process is started.

FIG. 37A and FIG. 37B illustrate the vertical incidence and the obliqueincidence, respectively, of ions displayed on the display/input unit 27.If the configuration as above is employed, it is possible to display, inan easily understandable manner, whether the processing in the plasmaprocessing apparatus 10 corresponds to either the vertical incidence orthe oblique incidence, which is convenient for a user of the plasmaprocessing apparatus 10.

Further, it is also possible to display, on the display/input unit 27, atiming of the vertical incidence and the oblique incidence of ions. Forexample, when switching the vertical incidence and the obliqueincidence, a red mark and a green mark are alternately blinked on thedisplay/input unit 27.

Further, it is also possible to display, at a time of setting theprocess condition, the incident direction of ions by an arrow mark onthe display/input unit 27. At this time, it becomes convenient for auser if an angle of the arrow mark is changed by being corresponded tothe incident direction of ions.

Further, it is also possible to design such that the arrow mark isdisplayed as an icon, and when the icon is touched, the incident angleis displayed by a numeric value. Further, it is also possible to designsuch that the displayed numeric value is set as an icon, and when thenumeric value is touched, the numeric value can be changed.

Examples

Hereinafter, examples will be described.

FIG. 38A to FIG. 38C, and FIG. 39A to FIG. 39C are graphs eachillustrating a result of plasma simulation of angle distributions ofions II which are incident on the wafer Wf in the plasma processingapparatus 10. The above-described simulation is conducted regarding ahalf area from a center of the plasma processing apparatus 10 by usingcommercially available software (VizGlow). Incident amounts of ions IIover one period of the RF low-frequency voltage are integrated tocalculate the angle distribution of the ions incident on the substrate.

FIG. 40 illustrates an electric field distribution of an entirecalculation area. Electric fields with respect to the arranged electrodeelements E are indicated by arrow marks. Further, a center O of thewafer Wf, and a later-described evaluation point P3 are illustrated.

FIG. 41 illustrates evaluation points P1 to P5 with respect to theelectrode element E. Ions which are incident on the wafer Wf right abovethe evaluation points P1 to P5 are evaluated. Specifically, electricfields on both sides of the electrode element E1 are evaluated.

Note that there is a strong electric field due to an edge effect in thevicinity of an end portion of the electrode element E, which exerts aninfluence on an evaluation of the oblique component, so that theelectric field in the vicinity of the center of the wafer Wf isevaluated.

Graphs G1 to G5 in each of FIG. 38A to FIG. 38C correspond to theevaluation points P1 to P5.

FIG. 38A illustrates a result when the electrode width W is 2 mm, theelectrode interval D is 4 mm, and only the RF low-frequency voltage Vbis turned on or off. The evaluation points P1 and P5, and the evaluationpoints P2 and P4 are respectively positioned symmetric in the right andleft directions with respect to a center of the electrode (evaluationpoint 3). It can be understood that, with respect to one electrode, theangle distributions at symmetric positions are approximately symmetric(signs are opposite, and angle peak positions are approximately thesame). Therefore, a good process uniformity can be achieved on theentire wafer Wf.

The reason why the angle distributions are not perfectly symmetric inthe right and left directions is because there is a distribution in aplasma density in the present simulation, and thus a bias in the obliquecomponent according to the distribution is caused. When the plasmadensity is uniform in the entire wafer Wf, symmetric angle distributionsare provided.

FIG. 38B illustrates a result when the electrode width W is 3 mm, andthe electrode interval D is 3 mm. An incidence of oblique ions having apeak at 0 to 5 degrees is confirmed. Also in this case, the right andleft distributions are close to symmetric distributions, so that theuniformity in the entire wafer is good.

FIG. 38C illustrates a result when the electrode width W is 1 mm, andthe electrode interval D is 1 mm. The peak angle of the obliquecomponent is about 1 to 2 degrees, and thus it can be understood thatthe incidence is close to the vertical incidence. Specifically, wheneach of the electrode width W and the electrode interval D is small, thegenerated oblique component becomes weak.

Explanation will be made on a dielectric constant of a dielectric.

FIG. 39A to FIG. 39C illustrate results obtained by changing adielectric constant of a dielectric member disposed in the electrodeinterval D. Here, the electrode width W is set to 2 mm, the electrodeinterval D is set to 4 mm, and a relative dielectric constant is changedin three ways of 1, 7.7, and 14.

As illustrated in FIG. 39A, when the relative dielectric constant is 1,the oblique component is not generated almost at all. In a medium withsmall dielectric constant, a potential drop is large. Therefore, apotential difference between adjacent electrode elements E becomes smallbefore it reaches the wafer Wf.

As illustrated in FIG. 39B and FIG. 39C, in the cases where the relativedielectric constants are 7.7 and 14, a potential difference betweenadjacent electrodes is maintained until when it reaches the wafer Wf,resulting in that oblique ions are incident. In each of the above cases,preferable distributions close to distributions symmetric in the rightand left directions and having peaks at about ±5 degrees, are obtained.

From the above description, it can be understood that the dielectricconstant is preferably large to some degree, although depending on theelectrode width W and the electrode interval D.

An effective range regarding the electrode width W and the electrodeinterval D will be described.

The oblique ions are effectively incident when an aspect ratio of adepth of hole becomes 20 or more, and an angle of up to about 5 degreescontributes to an improvement in shape of a bottom portion of the holeH. If processing of hole or trench in a conventional range in which theaspect ratio is smaller than the aforementioned aspect ratio isconducted, only the conventional vertical processing method can beemployed to deal with the processing.

FIG. 42A to FIG. 42C are graphs each illustrating a result of plasmasimulation of angle distributions of ions II which are incident on thewafer Wf in the plasma processing apparatus 10.

FIG. 43 illustrates evaluation points Q1 to Q5 with respect to thedielectric member DM. Ions which are incident on the wafer Wf rightabove the evaluation points Q1 to Q5 are evaluated. Specifically,electric fields on both sides of one dielectric member DM are evaluated.

FIG. 42A to FIG. 42C illustrate the angle distributions when both of theRF high-frequency voltage Va and the RF low-frequency voltage Vb areapplied by being turned on or off. The electrode interval D is fixed (2mm), and the electrode width W is changed to 1, 4, and 7 mm.

Graphs G1 to G5 in each of FIG. 42A to FIG. 42C correspond to theevaluation points Q1 to Q5.

It can be understood that when the electrode width W is 1 mm, theoblique component is not generated almost at all, and the incidence isclose to the vertical incidence. It can be understood that when theelectrode width W is 4 mm, a distribution having a definite peak isprovided, and when the electrode width W is 7 mm, the definite peak iseliminated in the angle distribution, and further, an etching rate islowered. As described above, the electrode width W has an appropriaterange.

FIG. 44 illustrates a relation between the electrode width W and thepeak angle, and FIG. 45 illustrates a relation between the electrodeinterval D and the peak angle.

An absolute value of the peak angle becomes large as the electrode widthW and the electrode interval D increase. It can be understood that eachof the electrode width W and the electrode interval D is preferablyabout 1 to 5 mm (more preferably, about 2 to 5 mm).

This can be explained as follows based on a reason why the obliquecomponent is generated. Specifically, a sheath of the plasma PL on thewafer Wf is curved by corresponding to a curve of the potentialdistribution. When the ions are vertically incident with respect to thecurved sheath, the ions are obliquely incident on the wafer Wf.

For example, in a capacitive coupling type plasma (CCP) process in whichthe electrode interval is 3 cm, a sheath thickness is typically about 1to 5 mm.

When each of the electrode width W and the electrode interval D issmaller than about 1 mm, a spatial deformation scale of sheath becomessmaller than the sheath thickness, resulting in that the deformation ofsheath is eliminated. Specifically, the oblique component is notgenerated or becomes weak.

Further, it is also not preferable that each of the electrode width Wand the electrode interval D is larger than about 5 mm. First, when theelectrode width is large, the electric field is constantly directedvertically to the wafer Wf on the electrode, and thus ions areconstantly incident vertically. When the electrode interval D is large,the electric field becomes weak on the whole, resulting in that theplasma density is lowered, and the process rate is lowered. Therefore,the electrode width W of 2 to 5 mm and the electrode interval D of about2 to 5 mm, are conditions suitable for the oblique incidence process.

Although not illustrated, according to simulations, also when the waferWf is rotated, a result which is approximately the same as that of thecase where the wafer Wf is not rotated (FIG. 38A to FIG. 38C, FIG. 39Ato FIG. 39C, and FIG. 42A to FIG. 42C) is obtained.

While certain embodiments have been described, these embodiments havebeen presented by way of example only, and are not intended to limit thescope of the inventions. Indeed, the novel embodiments described hereinmay be embodied in a variety of other forms; furthermore, variousomissions, substitutions and changes in the form of the embodimentsdescribed herein may be made without departing from the spirit of theinventions. The accompanying claims and their equivalents are intendedto cover such forms or modifications as would fall within the scope andspirit of the inventions.

1. A plasma processing apparatus, comprising: a chamber; an introducingpart configured to introduce a process gas into the chamber; a substrateelectrode disposed in the chamber and configured to mount a substratedirectly or indirectly thereon, the substrate electrode including aplurality of first and a plurality of second electrode elementsalternately arranged; a high-frequency power source configured to outputa high-frequency voltage of 40 MHz or more for ionizing the process gasto generate plasma; a low-frequency power source configured to output alow-frequency voltage of 20 MHz or less for introducing ions from theplasma; and a switching mechanism configured to apply the low-frequencyvoltage alternately to the first and the second electrode elements. 2.The plasma processing apparatus of claim 1, wherein the switchingmechanism applies a voltage in which the low-frequency voltage and thehigh-frequency voltage are superposed, alternately to the first and thesecond electrode elements.
 3. The plasma processing apparatus of claim1, further comprising a counter electrode facing the substrateelectrode, wherein the high-frequency voltage is applied to the counterelectrode.
 4. The plasma processing apparatus of claim 1, wherein thesubstrate electrode further includes a plurality of third electrodeelements disposed between the first and the second electrode elements;and wherein the plasma processing apparatus further comprises a secondhigh-frequency power source configured to apply a second high-frequencyvoltage for stabilizing the plasma to the third electrode elements. 5.The plasma processing apparatus of claim 1, wherein the substrateelectrode includes a plurality of dielectric members disposed at leastbetween the first and the second electrode elements.
 6. The plasmaprocessing apparatus of claim 5, wherein dielectric constants of thedielectric members are 7 or more.
 7. The plasma processing apparatus ofclaim 5, wherein the dielectric members have plate shapes; and whereinthe first and the second electrode elements include a plurality ofconductive layers disposed on the dielectric members.
 8. The plasmaprocessing apparatus of claim 1, wherein widths of the first and thesecond electrode elements are not less than 1 mm nor more than 5 mm; andwherein intervals between the first and the second electrode elementsare not less than 1 mm nor more than 5 mm.
 9. The plasma processingapparatus of claim 1, wherein the switching mechanism includes: a firstswitch configured to switch a connection state between the firstelectrode elements and the low-frequency power source; a second switchconfigured to switch a connection state between the second electrodeelements and the low-frequency power source; and a switch controllerconfigured to control the first and the second switch.
 10. The plasmaprocessing apparatus of claim 9, wherein the switch controller controlsthe first and the second switch so as to connect ones of the first andthe second electrode elements to a ground when the others of the firstand the second electrode elements are connected to the low-frequencypower source.
 11. The plasma processing apparatus of claim 9, whereinthe switch controller configured to control the first and the secondswitch so as to repeat a first to a fourth state in sequence, the firststate being defined by the first electrode elements connected to thelow-frequency power source, and the second electrode elements notconnected to the low-frequency power source; the second state beingdefined by both of the first and the second electrode elements connectedto the low-frequency power source; the third state being defined by thefirst electrode elements not connected to the low-frequency powersource, and the second electrode elements connected to the low-frequencypower source; and the fourth state being defined by both of the firstand the second electrode elements connected to the low-frequency powersource.
 12. The plasma processing apparatus of claim 1, wherein thesubstrate electrode includes a plurality of electrode elements arrangedin lines in two directions; and wherein the plasma processing apparatusfurther comprises a selecting mechanism configured to select the firstand the second electrode elements from the plurality of electrodeelements.
 13. The plasma processing apparatus of claim 12, wherein theselecting mechanism repeatedly selects the first and the secondelectrode elements so as to rotate directions of arranging the first andthe second electrode elements.
 14. The plasma processing apparatus ofclaim 1, wherein the switching mechanism switches a first and a secondstate in accordance with a progress of processing, the first state beingdefined by the low-frequency voltage applied alternately to the firstand the second electrode elements, the second state being defined by thelow-frequency voltage applied to both of the first and the secondelectrode elements.
 15. The plasma processing apparatus of claim 1,wherein the switching mechanism changes a period of alternatelyapplication of the low-frequency voltage to the first and the secondelectrode elements in accordance with a progress of processing.
 16. Theplasma processing apparatus of claim 1, further comprising a rotatingmechanism configured to relatively rotate between the substrate and thesubstrate electrode.
 17. The plasma processing apparatus of claim 16,wherein a period T of switching the first and the second electrodeelements is not 0.5n times a period Tr of the rotation, where n:integer.
 18. (canceled)